scholarly journals Fisheries impacts on lake ecosystem structure in the context of a changing climate and trophic state

2017 ◽  
Author(s):  
Tiina Nõges ◽  
Orlane Anneville ◽  
Jean Guillard ◽  
Juta Haberman ◽  
Ain Järvalt ◽  
...  
Keyword(s):  
Water Quality ◽  
Trophic State ◽  
Scale Effects ◽  
Trophic Levels ◽  
Interactive Effects ◽  
Phosphorus Loading ◽  
Lake Ecosystem ◽  
Ecosystem Structure ◽  
Top Down ◽  
Lake Basins

<p>Through cascading effects within lake food webs, commercial and recreational fisheries may indirectly affect the abundances of organisms at lower trophic levels, such as phytoplankton, even if they are not directly consumed. So far, interactive effects of fisheries, changing trophic state and climate upon lake ecosystems have been largely overlooked. Here we analyse case studies from five European lake basins of differing trophic states (Lake Võrtsjärv, two basins of Windermere, Lake Geneva and Lake Maggiore) with long-term limnological and fisheries data. Decreasing phosphorus concentrations (re-oligotrophication) and increasing water temperatures have been reported in all five lake basins, while phytoplankton concentration has decreased only slightly or even increased in some cases. To examine possible ecosystem-scale effects of fisheries, we analysed correlations between fish and fisheries data, and other food web components and environmental factors. Re-oligotrophication over different ranges of the trophic scale induced different fish responsesIn the deeper lakes Geneva and Maggiore, we found a stronger link between phytoplankton and planktivorous fish and thus a more important cascading top-down effect than in other lakes. This connection makes careful ecosystem-based fisheries management extremely important for maintaining high water quality in such systems. We also demonstrated that increasing water temperature might favour piscivores at low phosphorus loading, but suppresses them at high phosphorus loading and might thus either enhance or diminish the cascading top-down control over phytoplankton with strong implications for water quality.</p>

scholarly journals Assessment of Trophic Responses of a Reservoir to Seasonal and Annual Variations in Monsoon

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2117
Author(s):  
Su-mi Kim ◽  
Hyun-su Kim
Keyword(s):  
Water Quality ◽  
Trophic State ◽  
Monsoon Season ◽  
Phytoplankton Growth ◽  
Phosphorus Loading ◽  
Nutrient Concentrations ◽  
Trophic State Index ◽  
Post Monsoon ◽  
Post Monsoon Season ◽  
State Index

The variations in water quality parameters and trophic status of a multipurpose reservoir in response to changing intensity of monsoon rain was investigated by applying a trophic state index deviation (TSID) analysis and an empirical regression model to the data collected in two periods from 2014 to 2017. The reservoir in general maintained mesotrophic conditions, and Carlson’s trophic state index (TSIc) was affected most by TSITP. Nutrient concentrations, particularly phosphorus, did not show strong correlations with precipitation, particularly in the period with weak monsoon, and a significant increase in total phosphorus (TP) was observed in Spring 2015, indicating the possibility of internal phosphorus loading under decreased depth and stability of water body due to a lack of precipitation. TSIChl was higher than TSISD in most data in period 1 when a negligible increase in precipitation was observed in the monsoon season while a significant fraction in period 2 showed the opposite trend. Phytoplankton growth was not limited by nutrient limitation although nutrient ratios (N/P) of most samples were significantly higher than 20, indicating phosphorus-limited condition. TSID and regression analysis indicated that phytoplankton growth was limited by zooplankton grazing in the Spring, and that cell concentrations and community structure in the monsoon and post-monsoon season were controlled by the changing intensity of the monsoon, as evidenced by the positive and negative relationships between community size and cyanobacterial population with the amount of precipitation in the Summer, respectively. The possibility of contribution from internal loading and an increase in cyanobacterial population associated with weak monsoon, in addition to potential for nutrient enrichment in the post-monsoon season, implies a need for the application of more stringent water quality management in the reservoir that can handle all potential scenarios of eutrophication.

scholarly journals Decoupled taxonomic and ecological recoveries from the Permo-Triassic extinction

2018 ◽  
Vol 4 (10) ◽  
pp. eaat5091 ◽  
Author(s):  
Haijun Song ◽  
Paul B. Wignall ◽  
Alexander M. Dunhill
Keyword(s):  
Time Scales ◽  
Carrying Capacity ◽  
Mass Extinction ◽  
Marine Species ◽  
Taxonomic Diversity ◽  
Marine Ecosystems ◽  
Trophic Levels ◽  
Ecosystem Structure ◽  
Top Down ◽  
Structure Building

The Permian-Triassic mass extinction was the worst crisis faced by life; it killed >90% of marine species in less than 0.1 million years (Ma). However, knowledge of its macroecological impact over prolonged time scales is limited. We show that marine ecosystems dominated by non-motile animals shifted to ones dominated by nektonic groups after the extinction. In Triassic oceans, animals at high trophic levels recovered faster than those at lower levels. The top-down rebuilding of marine ecosystems was still underway in the latest Triassic, ~50 Ma after the extinction, and contrasts with the ~5-Ma recovery required for taxonomic diversity. The decoupling between taxonomic and ecological recoveries suggests that a process of vacant niche filling before reaching the maximum environmental carrying capacity is independent of ecosystem structure building.

scholarly journals Fish and seagrass communities vary across a marine reserve boundary, but seasonal variation in small fish abundance overshadows top-down effects of large consumer exclosures

2018 ◽  
Author(s):  
James Douglass ◽  
Richard Paperno ◽  
Eric A. Reyier ◽  
Anson H. Hines
Keyword(s):  
Seasonal Variation ◽  
Trophic Levels ◽  
Fish Abundance ◽  
Predatory Fish ◽  
Gut Contents ◽  
Spatial And Temporal Variation ◽  
Small Fish ◽  
Ecosystem Structure ◽  
Top Down ◽  
Exclusion Experiment

A growing number of examples indicate that large predators can alter seagrass ecosystem structure and processes via top-down trophic interactions. However, the nature and strength of those interactions varies with biogeographic context, emphasizing the need for region-specific investigations. We investigated spatial and temporal variation in predatory fish and seagrass communities across a Marine Protected Area (MPA) boundary in the Banana River Lagoon, Florida (USA), assessing trophic roles of intermediate consumers, and performing a large-consumer exclusion experiment in the MPA. Large, predatory fishes were most abundant within the MPA, while some mid-sized fishes were more abundant outside it. Small, seagrass-resident fishes, epifaunal invertebrates, and macrophytes also differed across the MPA boundary, but varied more among individual sites and seasonally. We cannot conclusively attribute these patterns to MPA status because we lack data from prior to MPA establishment and lack study replication at the level of MPA. Nevertheless, other patterns among our data are consistent with hypothesized mechanisms of top-down control. E.g., inverse seasonal patterns in the abundance of organisms at adjacent trophic levels, coupled with stable C and N isotope and gut contents data, suggest top-down control of crustacean grazers by seasonal recruitment of small fishes. Large-consumer exclosures in the MPA increased the abundance of mid-sized predatory and omnivorous fishes, but had few impacts on lower trophic levels. Results suggest that large-scale variation in large, predatory fish abundance in this system does not strongly affect seagrass-resident fish, invertebrate, and algal communities, which appear to be driven more by habitat structure and seasonal variation in small fish abundance.

scholarly journals The trophic spectrum: theory and application as an ecosystem indicator

2005 ◽  
Vol 62 (3) ◽  
pp. 443-452 ◽  
Author(s):  
Didier Gascuel ◽  
Yves-Marie Bozec ◽  
Emmanuel Chassot ◽  
Audrey Colomb ◽  
Martial Laurans
Keyword(s):  
Trophic Level ◽  
Trophic Structure ◽  
Fish Assemblages ◽  
Marine Protected Area ◽  
New Caledonia ◽  
Theoretical Background ◽  
Trophic Levels ◽  
Total Biomass ◽  
Ecosystem Structure ◽  
Top Down

Abstract Trophic spectra represent the distribution of biomass, abundance, or catch by trophic level, and may be used as indicators of the trophic structure and functioning of aquatic ecosystems in a fisheries context. As a theoretical background, we present a simple ecosystem model of biomass flow reflecting predation and ontogenetic processes. Biomass trophic spectrum of total biomass can be modelled as the result of three major factors and processes: trophic efficiency, transfer kinetics, and extent of top-down control. In the simulations, changes in the spectrum highlight fishing impacts on trophic structure and reveal some functional characteristics of the underlying ecosystem. As examples of potential applications, three case studies of trophic spectra are presented. Catch trophic spectra allow description of structural differences among European fishing areas and periods. Abundance trophic spectra of coral-reef fish assemblages display different trophic signatures, characterizing different reef habitats in New Caledonia and highlighting fishing effects in a marine protected area context. Biomass trophic spectra of demersal resources off Northwest Africa show a shift in ecosystem structure that can be attributed to the rapid increase in fishing pressure during the past few decades. Off Senegal, total biomass remained fairly constant, suggesting a strong top-down control linked to fisheries targeting high trophic level species. Off Guinea, exploitation rates are spread over a wider range of trophic levels, and the total biomass of demersal resources tended to decrease. The trophic spectrum is concluded to be a useful indicator describing and comparing systems in time and space, detecting phase shifts linked to natural or anthropogenic perturbations, and revealing differences in ecosystem functioning.

scholarly journals Common carp disrupt ecosystem structure and function through middle-out effects

2017 ◽  
Vol 68 (4) ◽  
pp. 718 ◽  
Author(s):  
Mark A. Kaemingk ◽  
Jeffrey C. Jolley ◽  
Craig P. Paukert ◽  
David W. Willis ◽  
Kjetil Henderson ◽  
...  
Keyword(s):  
Common Carp ◽  
Trophic Ecology ◽  
Experimental Studies ◽  
Structure And Function ◽  
Trophic Levels ◽  
Ecosystem Structure ◽  
Top Down ◽  
Bottom Up ◽  
And Function ◽  
Ecosystem Structure And Function

Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and non-unidirectional trophic interactions. The common carp (Cyprinus carpio) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes.

A Study on Relationship between Biomass of Macrophytes and the Health Status of the Lake Ecosystem

2012 ◽  
Vol 209-211 ◽  
pp. 1166-1169
Author(s):  
Yi Xin Xu ◽  
Hua Yong Zhang ◽  
Tou Sheng Huang ◽  
Yang Su
Keyword(s):  
Water Quality ◽  
Health Status ◽  
Trophic State ◽  
Ecological Indicators ◽  
Shandong Province ◽  
Lake Ecosystem ◽  
Health State ◽  
Eutrophication Assessment

Two ecological indicators, exergy (Ex) and structural exergy (Exst), and two ecological indexes, biodiversity and trophic state are calculated using the parameters of water quality and plankton investigated in five different ponds in Shandong province in China. The exergy and structural exergy are applied to evaluate the health state of ecosystems of the five ponds, whereas the biodiversity and trophic state are employed to make eutrophication assessment of the ponds. Via analyzing the relationships among the ecological indicators, the ecological indexes and the biomass of macrophytes, it is revealed that exergy, structural exergy and biodiversity is positive correlated to the biomass of macrophytes and that the trophic state decreases with the biomass of macrophytes. This result demonstrates that the ecosystems with more macrophytes can be regarded to hold better health state.

scholarly journals Critical Transitions in Lake Ecosystem State May Be Driven by Coupled Feedback Mechanisms: A Case Study from Lake Erhai, China

Water ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 85
Author(s):  
Rong Wang ◽  
John A. Dearing ◽  
Peter G. Langdon
Keyword(s):  
Positive Feedback ◽  
Feedback Loops ◽  
Trophic Levels ◽  
Lake Ecosystem ◽  
Ecosystem Structure ◽  
Critical Transitions ◽  
Lake Erhai ◽  
Time Lagged ◽  
Phosphorus Recycling ◽  
External Forces

Critical transitions between ecosystem states can be triggered by relatively small external forces or internal perturbations and may show time-lagged or hysteretic recovery. Understanding the precise mechanisms of a transition is important for ecosystem management, but it is hampered by a lack of information about the preceding interactions and associated feedback between different components in an ecosystem. This paper employs a range of data, including paleolimnological, environmental monitoring and documentary sources from lake Erhai and its catchment, to investigate the ecosystem structure and dynamics across multiple trophic levels through the process of eutrophication. A long-term perspective shows the growth and decline of two distinct, but coupled, positive feedback loops: a macrophyte-loop and a phosphorus-recycling-loop. The macrophyte-loop became weaker, and the phosphorus-recycling-loop became stronger during the process of lake eutrophication, indicating that the critical transition was propelled by the interaction of two positive feedback loops with different strengths. For lake restoration, future weakening of the phosphorus-recycling loop or a reduction in external pressures is expected to trigger macrophyte growth and eventually produce clear water conditions, but the speed of recovery will probably depend on the rates of feedback loops and the strength of their coupling.

scholarly journals Assessment of the water quality and trophic state of the Ribeirão Guaraçau Watershed, Guarulhos (SP): a comparative analysis between rural and urban areas

2018 ◽  
Vol 13 (2) ◽  
pp. 1 ◽  
Author(s):  
Reinaldo Romero Vargas ◽  
Márcia Da Silva Barros ◽  
Antonio Roberto Saad ◽  
Regina De Oliveira Moraes Arruda ◽  
Fernanda Dall'Ara Azevedo
Keyword(s):  
Water Quality ◽  
Total Phosphorus ◽  
Surface Waters ◽  
Urban Areas ◽  
Trophic State ◽  
Sewage Treatment ◽  
Trophic Levels ◽  
E Coli ◽  
Rural And Urban Areas ◽  
Rural And Urban

The urbanization process through which large urban centers have been passing has affected drastically the availability and especially the quality of water. The Ribeirão Guaraçau Watershed, located in the northern part of the Guarulhos municipality, includes rural and urban areas of different land-use classes. The goal of this study is to assess the water quality and to diagnose the eutrophication stage of the surface waters of the Ribeirão Guaraçau, the main water course of the Ribeirão Guaraçau Watershed. To assess environmental quality, physical-chemical analyses (temperature, pH, turbidity, conductivity, and total phosphorus) and microbiological analyses (E. coli) were carried out during a period of 12 months. The Trophic State Index (TSI) was used to ascertain the environmental degradation conditions of lotic and lentic environments. The surface waters of the Ribeirão Guaraçau in the rural area are already compromised, with worsening of the water quality upstream indicated by high total phosphorus and E. coli caused by fecal contamination due to lack of basic sanitation in the region. Characteristic sites of the rural areas already present signs of degradation with trophic levels varying from oligotrophic to hypereutrophic. The need to provide sewage collectors and sewage treatment systems at the Bonsucesso Sewage Treatment Station, inaugurated in 2011, and the control of the occupation in areas that produce good quality water is paramount.

scholarly journals Assessing Impacts of Changes in External Nutrient Loadings on a Temperate Chinese Drinking Water Reservoir

2021 ◽  
Vol 9 ◽  
Author(s):  
Qingchuan Chou ◽  
Anders Nielsen ◽  
Tobias K. Andersen ◽  
Fenjuan Hu ◽  
Weiyu Chen ◽  
...  
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Nutrient Loading ◽  
Water Reservoir ◽  
Phosphorus Loading ◽  
Lake Ecosystem ◽  
Nutrient Load ◽  
Nutrient Inputs ◽  
Nutrient Loadings ◽  
External Nutrient

The safety of drinking water is constantly being evaluated. In the last few decades, however, many drinking waters sources in the world, including in China, have undergone serious eutrophication and consequently water quality deterioration due to anthropogenic induced stressors such as elevated external nutrient inputs. In this study, we used the state-of-the-art complex, dynamic, mechanistic model GOTM-FABM-PCLake (a coupled one-dimensional hydrodynamic-lake ecosystem model) to quantitatively assess the impacts of external nutrient loading on the temperate Jihongtan reservoir in Shandong Province, China. Simulated values of all variables targeted in calibration (water temperature, dissolved oxygen, total nitrogen, total phosphorus, and chlorophyll a) agreed well with observations throughout the entire calibration and validation period and generally mimicked seasonal dynamics and inter-annual variations as found in the monitoring data. A series of scenarios, representing changed external nutrient loadings (both increasing and decreasing compared to the current nutrient load), were set up to quantify the effects on the reservoir water quality. Changes relative to the current external nutrient load had a significant effect on the simulated TN and TP concentrations in the reservoir. Our impact assessment indicate that TN will meet the Chinese water quality requirements of the water source (Class III) when the external nitrogen load is reduced by 70%, whereas TP will meet the requirements even if the external phosphorus load is increased by 100% relative to current loads. The model predicts progressively higher summer and autumn phytoplankton biomasses in the scenarios with increasing external phosphorus loading and potential toxic cyanobacteria will become more dominant at the expense of diatoms and other algae. Strict control of the external nutrient loading is therefore needed to maintain good drinking water quality in the reservoir.

Tejo 1– An Interactive Program for the Division of Estuaries into Homogeneous Areas

1987 ◽  
Vol 19 (9) ◽  
pp. 43-51 ◽  
Author(s):  
A. S. Câmara ◽  
M. Cardoso da Silva ◽  
L. Ramos ◽  
J. Gomes Ferreira
Keyword(s):  
Water Quality ◽  
Computer Program ◽  
Heuristic Algorithm ◽  
Management Model ◽  
Interactive Program ◽  
Basin Management ◽  
Interactive Computer Program ◽  
Lake Basins

The division of an estuary into homogeneous areas from both hydrodynamic and ecological standpoints is essential to any estuarine basin management model. This paper presents an approach based on a heuristic algorithm to achieve such a division. The methodology implemented through an interactive computer program named Tejo 1 applies morphological, water quality and management criteria in order to achieve the disaggregation. The approach is equally applicable to river or lake basins, with only minor adaptations. An application of Tejo 1 to the Tejo estuary is included for illustrative purposes, which resulted in the final division of the estuary into 11 homogeneous areas.

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